What is the difference between nematodes and other worms?

Nematodes (also known as roundworms) form one of the largest phyla of animals. They are unsegmented, bilaterally symmetrical, cylindrical worms with a pseudocoelom (a fluid-filled body cavity not lined by mesothelium). Nematodes are found in all environments, including soil, fresh water, and marine habitats. They are also found in association with plants, animals, and fungi.

Nematodes differ from other worms in a number of ways:

- Body shape: Nematodes are typically long and thin, with a smooth, unsegmented body. Other worms, such as earthworms and flatworms, have a more complex body structure with segments or appendages.

- Pseudocoelom: Nematodes have a pseudocoelom, which is a fluid-filled body cavity that is not lined by mesothelium. Other worms, such as annelids and mollusks, have a true coelom, which is a fluid-filled body cavity that is lined by mesothelium.

- Digestive system: Nematodes have a simple digestive system, with a mouth and an anus. Other worms, such as flatworms and annelids, have a more complex digestive system with specialized structures for feeding and digestion.

- Nervous system: Nematodes have a simple nervous system, with a nerve ring around the esophagus and a pair of ventral nerve cords. Other worms, such as annelids and mollusks, have a more complex nervous system with a brain and ganglia.

- Reproductive system: Nematodes have a reproductive system with separate sexes, and most species are oviparous (egg-laying). Other worms, such as annelids and mollusks, may have a reproductive system with both male and female reproductive organs (hermaphroditic), and some species may be viviparous (live-bearing).

Examples of other worms:

- Annelids: earthworms, leeches

- Platyhelminthes: tapeworms, flukes

- Nematomorphs: horsehair worms

- Rotifers: water bears